Barents Sea Ice edge position 1579-2018. Data not available; digitized and traslated by Bongo DIG command from Yndestad's blog post figure 7. The red line is the parabolic fit used for Lomb spectrum. Data are "as measured", without interpolation (no need of constant step) and filtering. The spectrum shows a fully normal 18.6 yr spectral peak and very little of the plaetora of sub- and super-harmonics listed by Yndestad (2019, blog page).